1. Field of the Invention
The present invention relates to a control apparatus for an internal combustion engine, provided with a variable valve timing mechanism (VVT) for variably controlling an opening/closing timing (valve timing) of an intake valve and an exhaust valve of the internal combustion engine in response to an operating condition of the engine, and more particularly to a control apparatus for an internal combustion engine for controlling a fuel injection amount or an ignition timing in response to a change in the valve timing.
2. Description of the Related Art
Conventionally, in a D-jetro type control apparatus for an internal combustion engine, a fuel injection amount or an ignition timing has been controlled by using a volumetric efficiency or ignition timing which has been obtained from the number of revolutions per minute (rpm) of the engine or an intake pressure. Thus, in the D-jetro system, the volumetric efficiency or the ignition timing is obtained by using the rpm of the engine and the intake pressure as parameters. The volumetric efficiency and the ignition timing are obtained at a plurality of points from a plurality of the rpms of the engines and intake pressures to thereby prepare a map, and values other than the values obtained in advance with respect to the volumetric efficiency and the ignition timing are obtained from the map by way of interpolation.
Such a method for obtaining the volumetric efficiency is effective in the case where the opening/closing timing of the exhaust/intake valve is kept constant. However, in the internal combustion engine provided with the VVT for variably and continuously controlling the valve timing, even if the rpm of the engine or the intake pressure is kept constant, a change in the opening/closing timing of the exhaust/intake valves causes a change in the volumetric efficiency or the optimum ignition timing. Then, the change in the volumetric efficiency and/or the ignition timing relative to the change of such valve timing is not constant depending upon the rpm of the engine or the intake pressure.
Accordingly, in the internal combustion engine provided with the VVT, in the case where the opening/closing timing of the exhaust/intake valve is changed, there arises a problem in that the fuel injection amount or the target ignition timing may be shifted from the optimum value.